Summary

Ask medieval historian Michael McCormick which year was the worst to be alive, and he's got an answer: "536." In that year, a mysterious fog plunged Europe, the Middle East, and parts of Asia into darkness, day and night—for 18 months. Summer temperatures dropped 1.5°C to 2.5°C, initiating the coldest decade in the past 2300 years. Snow fell that summer in China; crops failed; people starved. Historians have long known that the middle of the sixth century was a dark hour in what used to be called the Dark Ages, but the source of the mysterious clouds has long been a mystery. Now, after analyzing volcanic glass particles in ice from a Swiss glacier, a team of researchers has identified the culprit: A cataclysmic volcano in Iceland spewed ash across the Northern Hemisphere early in 536.